Point transects-Multi-species survey

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Estefania Isabel Muñoz Salas

Oct 25, 2022, 2:58:03 PM10/25/22
to distance-sampling

I am analyzing some bird data that were generated from 10-minute point counts in different habitat types, in different regions, from 2009 to 2018. But not all areas have data every year.
I was following the example of Montrave by Buckland ( 2006 ), for multispecies analysis. But I had a question. If you want to analyze point transect data, the variable Effort - length of the transect (km) that is used to correct effort in this exercise, what data should be used for the sampling points? I don´t have the length of the transects. 

Another doubt I have is whether, given that there are no data for each year in each region, the information should be filtered by region and year? As a way to standardize ? Or should I filter the data for specie instead? 

It is my first time analyzing this data, I really would appreciate your advice.


Eric Rexstad

Oct 26, 2022, 4:23:12 AM10/26/22
to Estefania Isabel Muñoz Salas, distance-sampling

Thanks for your questions. The answer to the first is easy, the answer to the second is not so easy.

Effort for point transects is measured by number of visits to the station. The column labelled "Effort" is the number of visits. If each station is visited a single time in a year, then all stations will have a "1" in the Effort column.  If you are using the "Distance" R package, examine some sample data sets provided with the package, such as wren_5min​ to see that each point in that study was visited twice.

Your second question has many facets. It is common for surveys of multiple species in multiple habitats over a number of years will not have adequate numbers of detections for all combinations of species/habitat/year. How to cope with this depends upon the purpose of the surveys; what question are you trying to answer. It might be best if we have a more detailed conversation off the email list regarding the specifics of your data and your questions. If we arrive at conclusions of interest to the wider distance sampling community, you can report the conclusions we reached. Happy to continue the discussion off list.

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Subject: [distance-sampling] Point transects-Multi-species survey
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